Electrical enclosures are cases used to protect the electrical components stored inside the enclosure. The electrical components are mounted on a backplane or backplate (backplane and backplate are used interchangeably) or panel that is secured or mounted to the interior of the enclosure case. The backplane may be predrilled with a series of openings to accommodate electrical components. Typical enclosures are rectangular boxes constructed of metals such as steel, or fiberglass or plastic. The enclosure generally has a top cover or door that can be opened to provide access to the electrical components mounted in the panel. The cover, when closed, provides a degree of protection for the electrical components against moisture and other adverse environmental conditions. Electrical wiring penetrates the enclosure typically through conduits or similar devices that are secured to the enclosure using specialized fittings.
Some enclosures include an inner swing panel or interior cover plate that is exposed when the enclosure cover is opened. The interior cover plate generally is mounted on the enclosure behind the door or enclosure cover. The interior cover plate or inner swing panel is used to mount switches, circuit breakers, gauges, lamps or other components that the operator may need to periodically access for various reasons, but still protect the electrical components mounted on the backplate. The interior cover plate can be moved to provide access to the interior of the enclosure. Generally, the inner swing panel is hingedly connected to the enclosure, but can be screw mounted, toggle mounted or otherwise removable. An example of such an enclosure is shown in FIG. 1. Shown are enclosure 1, cover 2, and interior swing panel 3. The interior swing panel 3 shown in FIG. 1 is hingedly mounted to the enclosure, as is the cover plate 2. To accommodate a hingedly mounted interior swing panel, many enclosures include an interior projection support bracket attached to the interior of the enclosure opposite the hinged side of the interior swing panel (not shown). This bracket is used to support the interior swing panel in a closed position.
In assembling an enclosure, the electrical components will be installed and wired as needed to the backplane. The backplane is then inserted into the interior of the enclosure and secured to the enclosure (usually, by corner screw mounts installed at suitable locations in the interior of the enclosure). The door components are added (either to the interior cover plate, inner swing panel or enclosure cover or both) as well as components mounted in the exterior of the enclosure (such as warning lamps, alarms or lightning arresters), and wired to the backplane as needed. The assembled enclosure is then transported to the field, where suitable enclosure cutouts are installed through the enclosure to accommodate the incoming conduits or other devices. In some instances the enclosure cutouts can be placed in the device in the assembly plant, if a high degree of tolerance is expected in the field installation.
The assembled enclosure is then mounted at its desired location, and conduits attached, providing power and control wiring to enter or exit the interior of the enclosure. Once the enclosure is assembled, mounted and conduits attached, removal of the outer enclosure is difficult, as the conduit must be disassembled and moved, and this may have to be initiated at a location remote from the enclosure. Hence, servicing of components in the enclosure generally entail field service of the components on the backplane while the backplane is installed. Removal of the backplane from a fully installed enclosure is very difficult or impossible. The conduits and other devices that are mounted on the exterior of the enclosure or the inner swing panel have an interior extent—that is, the conduit or other devices extends into the interior of the enclosure and presents a physical obstacle to lifting the backplane off the mounts and out of the interior. The backplane, to be removed, would require removal of the interior penetrations of the conduit or other exterior mounted devices, that is, a disassembly of the field mounting of the enclosure. In most cases this is not possible without undesirable lengthy shut down of equipment and excessive costs.
In instances where extensive re-hab of the electrical components are required (for instance, due to flooding) or where new designs require for extensive replacement of components, a complete new enclosure and backplane may be required in the field to “swap” out with the existing installed enclosure. Such a procedure is expensive and time consuming. It would be beneficial to be able to remove the backplane from the enclosure without disassembling the field mount. While the exterior electrical connections to the backplane would have to be broken, the integrity of the field mounted enclosure would not be broken. The ability to remove the backplane and the attached electrical components without disturbing the enclosure field mount is desirable.